The steep ramp test in youth: Reliability, validity and norm values

Background: The steep ramp test (SRT) is a bicycle exercise test protocol which does not require the use of respiratory gas analysis and is used in adults with cardio-pulmonary disease. However, reliability, validity and reference values in children are currently lacking. Therefore, the aim of this study was to study reliability, validity as well as provide reference values for SRT performance in healthy youth, aged 8 to 19 years. Methods: For the reliability, validity statistics, 75 children were randomly divided in a reliability group (n=37, 17 boys; age: 13.86±3.22 years) and a validity group (n=38, 17 boys; age: 13.85±3.20 years). Within two weeks, the reliability group performed two SRTs, whereas the validity group performed one SRT and one regular cardiopulmonary exercise test (CPET) with respiratory gas analysis. Data were analyzed using the intra class correlation coefficient (ICC), a Bland-Altman plot, linear regression analysis, and Pearson correlation coefficients. For the reference values, 252 children and adolescents, 118 boys (age: 13.4±3.0 years) and 134 girls (age: 13.4±2.9 years), performed a SRT. Peak work rate (WRpeak) was the primary performance criterion measured. Reference values were expressed as reference centiles developed using generalized additive models for location, scale, and shape. Results: Reliability statistics for the SRT showed an ICC of 0.986 for WRpeak. The average difference the two SRTs was -6.4 W, with limits of agreement between +24.5 W and -37.5 W. Validity: a high correlation between WRpeak achieved at the SRT and the peak oxygen uptake (VO2peak) attained during CPET was found (r=0.958; P